Controllable pitch propellers for marine vessels

ABSTRACT

In a controllable pitch propeller arrangement of the type having a hydraulic piston-and-cylinder type motor in the propeller hub for effecting pitch settings, the power oil is passed to and from the motor through oil tubes nested in the hollow propeller shaft, and the follow-up or feedback member, which gives read-out of actual pitch, is relatively isolated from the temperature effects of the power oil, preferably by arranging the follow-up or feedback member as the central member of a nested arrangement in which the power oil tubes are radially spaced from the feedback member about the circumference of the nested assembly. Preferably the feedback member and the oil tubes are arranged as a unitary bundle, made up of several sections, and the oil tubes of each section are provided with sliding seals at the section coupling, whereby thermal expansion and contraction of the oil tubes is absorbed by the sliding seals in each section and will not affect the overall length of the bundle or the feedback member, thus preventing or minimizing erroneous pitch feedback signals. The follow-up member preferably is tubular, and an air tube passes therethrough to feed air to the propeller blades.

[ 1 Dec.l1,1973

[ CONTROLLABLE PITCH PROPELLERS FOR MARINE VESSELS Peder K. Wennberg, Port Washington, NY.

[73] Assignee: Propulsion Systems, Inc., Port Washington, NY.

22 Filed: Apr. 13,1971

21 Appl. No.: 133,682

[75] lnventor:

Primary Examiner-Everette A. Powell, Jr. Att0mey-Larson, Taylor and l-linds [57] ABSTRACT In a controllable pitch propeller arrangement of the type having a hydraulic piston-and-cylinder type motor in the propeller hub for effecting pitch settings, the power oil is passed to and from the motor through oil tubes nested in the hollow propeller shaft, and the follow-up or feedback member, which gives read-out of actual pitch, is relatively isolated from the temperature effects of the power oil, preferably by arranging the follow-up or feedback member as the central member of a nested arrangement in which the power oil tubes are radially spaced from the feedback member about the circumference of the nested assembly. Preferably the feedback member and the oil tubes are arranged as a unitary bundle, made up of several sections, and the oil tubes of each section are provided with sliding seals at the section coupling, whereby thermal expansion andcontraction of the oil tubes is absorbedby the sliding seals in each section and will not affect the overall length of the bundle or the feedback member, thus preventing or minimizing erroneous pitch feedback signals. The follow-up member preferably is tubular, and an air tube passes therethrough to feed air to the propeller blades.

22 Claims, 9 Drawing Figures PATENIEB 1 3,778,187

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SHEET 5 0f 7 mvnmon PEDER K. WENNBERG ATTOII N IIYS saw 1 nr 7 mvzmon PEDER K. WENNBERG BY 071645040 Day/m w ATTORNEYS CONTROLLABLE PITCH PROPELLERS FOR MARINE VESSELS FIELD OF THE INVENTION This invention relates to controllable pitch propellers for marine vessels, and more particularly to controllable pitch propellers of the type wherein the pitch setting hydraulic motor is located in the propeller hub remote from the servo valve which controls the power oil for the motor, and wherein a follow-up or feedback member is coupled to the hydraulic motor to give instantaneous indication of read-out of actual pitch position. The position of a selected point on the follow-up member may be used to close a control valve when actual pitch conforms to ordered pitch, or to cancel out a pitch changing signal when the ordered pitch is reached, or merely to provide an indication of actual pitch setting, etc. Regardless of the particular function, it is important that the follow-up member accurately relfect the actual pitch setting of the blades.

BACKGROUND OF THE INVENTION Although there are various designs for controllable pitch propellers, probably the favored type is that with the hydraulic piston in the propeller hub, since this does not require long load carrying cranks or rods extending through the propeller shaft. Additionally, the hub diameter for this type is generally smaller, and there are less mechanical problems than having the piston in the main shaft. However, in perhaps all controllable pitch propellersin general, and this favored type inparticular, problems have been experienced in the accurate setting of pitch. In a relatively standard control arrangement for this type of propeller, a desired or ordered pitch output is achieved from a single lever control for the completeengine and propeller system, and this ordered value is compared with the actual value, and the error between the two is used to effect a pitch change to bring the two values or settings into conformity. The actual pitch setting or value is usually sensed automatically from the position of a follow-up or feedback meniberextending through the shaft between the hydraulic motor and the servo valve control box. For instance, in most controllable pitch propeller designs, where the servomotor is located in thehub, power oil is conveyed from pumps through an over-theshaft sealed servobox, and then through oil tubes located within the bore of the propeller shaft. These oil tubes usually ar'e -concentric, and form the major link in the mechanical feedback system. Instantaneous read-out of piston 'position, and hence pitch setting, is normally obtained through a yoke at the forward end of the oil tube assembly. When starting with cold oil,

growth in the feedback or follow-up link produces an error between the se'rvo motor piston and the servo control box linkage or other means used to detect actual pitch by sensing the position of the yoke. The effect of this error can be such as to alter the pitch by up to one and one-half degrees after maneuvering. Among other things, this makes it difficult to align the command control handle with the actual pitch position. With the control handle in the zero pitch position, it is possible because of the thermal expansion of the feedback member in a preset control to develop thrust ahead or astern, that is, to bring about a change in pitch without a change in ordered pitch. This may overload or underload the engines, and renders it extremely difficult to obtain proper load division in a twin screw vessel. lnfact, the problem is particularly severe in such twin screw vessels, since in a twin screw vessel it is not unusual, particularly in Naval vessels, to have unequal shaft lengths, and hence unequal lengths of feedback members and unequal feedback errors. This aggravates the feedback error between port and starboard propellers, and can cause vibration, unequal power distribution, etc.

In a typical controllable pitch propeller, the temperature of the power oil may be between and F, and perhaps 50 gallons of oil may be required to effect a maximum pitch stroke. This can cause a thermal growth of one-half to one inch in 100 feet of feedback link, with a temperature rise of 50 to 100F. This should be considered in light of the fact that the servo valve spool controlling the power oil, which valve is commonly coupled to the feedback link for control purposes, may be a negative lap valve such that a movement of only a few thousandths of an inch causes a pitch change.

With the increasing popularity of controllable pitch propellers, the problem has not gone without attention. Proposed solutions that have been given consideration range from accurate initial calibration (impractical even if possible) to temperature compensation by inserting a temperature dependent bias in the control system. However, adequate temperature compensation, although theoretically workable and simple, is difficult to achieve in practice. The difficulty lies primarily in the fact that different lengths of oil column must be displaced through the tubes during pitch changes of different amounts. For instance, a full pitchchange will displace the entire column of oil through a tube, whereas a partial pitch change may displace only apart of the column. Therefore, for pitch changes of different amounts, different lengths of the oil tubes are subjected to the hot oil, causing non-linear thermal expansion and contraction over the entire lengths of the oil tubes forming the feedback link.

In some applications of controllable pitch propellers an arrangement is needed for for conveying air to the propeller blades, where it .is discharged through orifices along, for instance, the leading edges of the blades. Such an arrangement is generally known as the Prairie air system, and its incorporation is usually required in such propellers for United States Navy constructions. Previous designs for bringing air down the shaft to the propeller blades have been rather complicated, involving the use of hoses, pipes, etc. A check valve is normally incorporated at each blade in the air passage, and those of which I am aware have been oriented generally radially relative to the rotational axis of the hub. The function of the check valves is to prevent sea water from entering the air passages from the propeller blades when the air system is hot in use. Because of the complexities of the previously known systems, and also because of what I consider to be dubious design solutions in some areas, substantial improvement is needed in this area, particularly to improve reliability, ease of maintenance, ease of fabrication and assembly, and compactness, together with the cost savings attendant to such improvements.

SUMMARY OF'THE INVENTION Basically, it is an object of this invention to provide a new and improved arrangement, in controllable pitch propellers of the type previously discussed, for conveying power oil from the servo valve box to the hydraulic motor in the propeller hub, which arrangement minimizes or avoids the problems caused by thermal expansion and contraction in the feedback link between the hydraulic motor and the servo control box or other means which require an accurate indication of actual pitch position. It is a further object of this invention to provide such an arrangement which does not require welding and straightening of long sections, as has been usually required in the prior art arrangements. It is a further object of the invention to provide such an arrangement wherein the power oil tubes and feedback link comprise a unit which is built up and can be easily and rigidly assembled during initial manufacture and subsequent maintenance. It is a further object of the invention to provide such a built up assembly which can be lighter in weight as compared with prior art arrangements of concentric tubes, and which can be more easily balanced with reference to rotative imbalance. It is still a further object of this invention to provide such an arrangement wherein the power oil tubes are basically free floating and can expand without affecting the overall length of the power oil tube assembly or the feedback link. It is still a further object of this invention to provide an improved arrangement for conveying air to the propeller blades, the improved arrangement being essentially hard coupled and not requiring any swivel joints or so-called dynamic seals within the hub and shaft system, or any flexible hoses, while at the same time allowing for free expansion of the tube conveying the air down the shaft; Furthermore, the improved arrangement utilizes check valves which are generally horizontally disposed, and thus not subject to the adverse effects of centrifugal force as are the known radially disposed valves.

Generally in accordance with this invention, the power oil is passed to and from the hydraulic motor in the hub through oil tubes in the shaft, and the follow-up or feedback member is relatively isolated from the temperature effects of the power oil. Preferably the followup member and the oil tubes are arranged as a unitary bundle of tubes, made up of several tube sections, with the power oil tubes nested circumferentially about and radially spaced from the centrally disposed follow-up tube, and the oil tubes of each section are provided with sliding seals, whereby thermal expansion and contraction of the oil tubes will not affect the overall length of the tube bundle or the follow-up member. The follow-up member thus is in a relatively stable temperature environment relative to the previously known arrangements, especially when one considers that the propeller shaft in which the assembly is located normally will be filled with hub oil which may bear a volume-to-volume ratio of perhaps to 1 relative to the power oil. Thus, any heat loss from the power oil in the oil tubes will be dissipated substantially throughout the larger hub oil volume, and any thermal expansion or contraction of the follow-up member caused by variations in hub oil temperature will be within acceptable limits for most applications. In any event, should even more precise control be desired or necessary, a temperature compensation bias could be incorporated in the control system, since th difficulties previously discussed in connection with compensating for power oil temperature would not apply to compensating for hub oil temperature. Such a temperature responsive bias might take the form of a temperature transducer electrically biassing a DC bridge circuit of the type disclosed in my prior US. Pat. No. 3,527,186. Alternatively, oil at a controlled temperature may be continuously circulated through or around the follow-up member over substantially its entire length. Such a circulating system could, in essence, preheat the oil tube to a predetermined temperature before getting the vessel underway, and thereafter would maintain the follow-up member at a pre-set temperature, and hence a predetermined length.

Preferably the follow-up member is tubular, and for applications where the air feed to the propeller blades is required, the air tube passes through the followup tube and is rigidly secured in the hub, thus providing for free relative movement between the air tube and the follow-up tube. Hard piping connections in the hub convey the air from the hub end of the air tubes to the blade disc, and generally horizontally disposed check valves are used. Any adverse thermal effects on the follow-up member from the air passing through the air tube can be minimized or avoided by wrapping the air tube with insulating tape and/or maintaining a circulating oil column at a controlled temperature in the annulus between the air tube and the follow-up tube to maintain a pre-set temperature for the follow-up tube. Alternatively, a temperature compensation bias could be automatically applied to the pitch control system when the air system is activated, since the air system operates continuously when it is activated, and thus would have a substantially continuous and stable effect on the follow-up tube.

The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiments presented below.

BRIEF DESCRIPTION OF THE DRAWINGS In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings, in which:

FIG. 1 is a simplified diagrammatic illustration of the basic features of the invention as embodied in a controllable pitch propeller arrangement of the type having the servo control box mounted on the drive gear box for the shaft.

FIGS. 2A and 2B together comprise a more detailed illustration of the same basic features as embodied in a controllable pitch propeller arrangement utilizing a shaft mounted servo control box, FIG. 2A showing the propeller hub and a stern shaft portion, and FIG. 28 showing the servo control box plus forward and middle shaft sections.

FIGS. 3 and 4 are enlarged detailed illustrations of couplings shown somewhat schematically in FIG. 2B.

FIG. is an enlargeddetailed illustration of a crossover or transitional coupling shown somewhat schematically in FIG. 2A.

FIG. 6 is a diagrammatic illustration corresponding generally to FIG. 1," but including also an arrangement for controlling thettemperature of the follow-up member by circulating controlled temperature oil continuously therethrough.

FIG. 7 is a sectional view taken long lines 7-7 of FIG. 6 or FIG.8.

FIG. 8 is a more detailed sectional view of an exemplary arrangement: for passing the circulating oil into and extracting it from the follow-up member.

Because controllable pitch propellers and the controls therefor are well known, the present description will be directed in particular to elements forming part of, or cooperating' more directly with, the present invention, it being understood that propeller and control details not specifically shown or-described may take various forms well known to those skilled in the art.

Referring to theschematic illustration shown in FIG. 1, a propeller hub l carrying controllable pitch propeller blades 2 is mounted at the end of a propeller shaft 3,"which is coupled to a conventional reduction gear 4. A servo valve box 5 is mounted on reduction gear 4. The pitch changing mechanism in hub l and the control valve arrangement in servo box 5 may be considered as standard, corresponding, for instance, to Liaaen type DG or EG controllable pitch propellers, sold by Propulsion Systems, Inc., of Port Washington, New York. In these type designations, a D type pitch changing*mechanism incorporates a double crank driving connection between the hydraulic motor and the propeller blade, and the type E mechanism utilizes a single crankdriving connection. The G type servo designates a reduction gear mounted arrangement, as opposed to a shaft mounted servo box. Furthermore, an exemplary pitch changing mechanism in the hub is shown in FIGS. 4--6 of US; Pat. No. 3,171,494, (Liaaen), and an exemand 13.Tube 9 is coupledto piston 7 and cross-over or transitional coupling 14, and tube 8 is coupled to coupling 14, wherebythe entire assembly in the hollow shaft 3 is causedto move with piston 7. Oil tubes 10 and 11 are coupled rigidly to cross-over coupling 14 at one end, and areslidably mounted in tube bundle support 15 attheir other ends. In the same manner, oil

tubes 10' and 11' are coupled at their stern ends to tube bundle support 15, and slidably mounted at their forward ends in cross-over or transitional coupling 16.

Inner and outer oil tubes 13 and 12 are coupled to cross-over coupling 16, andare slidably and rotatably mounted in servo valve body 17.

Valve 17 is of a known type, comprising servo valve spool 18 which is positioned hydraulically by pilot valve 19 to connect oil passages 21 and 22 to power oil inlet 20 or to drain. Reference is made to US. Pat. No. 3,527,186 for details-of an exemplary valve. Alternatively, the valve may beof the type shown in US. Pat.

No. 2,679,233, which discloses a mechanically stroked servo valve of the shaft mounted type, which does not differ in principle from a reduction gear mounted servo valve. Oil passage 21 communicates with outer oil tubes 12 and thence with oil tube 11' by way of crossover coupling 16, then with oil tube 11 by way of tube bundle support 15, and then at cross-over coupling 14 oil tube 11 communicates with the interior of piston rod/oil tube 9, and thence with the left-hand side of servo piston 7 through an opening in the piston. Oil passage 22 communicates with inner oil tube 13, thence with oil tubes 10' and 10 by way of cross-over coupling 16 and tube bundle support 15, and thence with oil tube 8 and the right-hand side of piston 7 by way of cross-over coupling 14. Therefore, when power oil inlet 20 is connected to oil passage 21, the piston will move to the right, oil passage 22 then being connected to drain. Reverse action occurs when the oil passages are connected differently by the valve spool 18.

Pitch actuator 23 mounted on tube 8 is coupled to a crank pin 25 carried by thecrank disc of propeller blade 2 through a connecting rod or the like schematically shown at 24, whereby movement of the piston 7 will vary the pitch setting of blade 2.

Movement of the piston is also followed by feedback or follow-up tube 26, consisting of a plurality of sections rigidly coupled together at couplings 14, 15 and 16, and passing freely through the servo valve body 17. A follow-up spool or yoke 27 is mounted on follow-up tube 26, and is coupled with pilot valve 19 through a follow-up linkage schematically shown at 28. Followup linkage'28 is a standard differential lever linkage as commonly used in systems of this type, exemplarly differential lever arrangements beingshown in US. Pat. Nos. 2,679,233 and 3,527,186. A command pitch actuator is indicated schematically at 32, and is coupled to the follow-up lever 28 by a schematically illustrated linkage 33. For purposes of this invention, command pitch actuator 32 may be considered as directly manaully operated, although in most actual constructions pitch actuator 32 will be part of a conventional electrical repeater system linked electrically with a command control of the bridge, or, as disclosed in US. Pat. No. 3,527 ,186, actuator 32 may be an electric motor controlled by a DC bridge network consisting of a pitch command potentiometer on the bridge and a feedback potentiometer having its wiper coupled with actuator 32 so as to move therewith, whereby a command pitch setting on the bridge potentiometer will unbalance the bridge and cause actuator 32 to be driven in the sense to rebalance thebridge such arrangements arewell known in the art, and do not form a novel feature of the instant invention.

Basically, the apparatus described thus far operates in the same manner as previously known devices. Thus, when a particular pitch setting is desired, actuator 32 is moved or driven so as to pivot follow-up lever 28 about its coupling with spool 27, thus stroking pilot valve 19, which in turn hydraulically strokes servo valve spool 18. This opens either passage 21 or 22 to power oil inlet 20, simultaneously connecting the other passage to drain, and driving servo piston 7 appropriately to move the blade 2 to the commanded pitch setting, through actuator 23, coupling 24, and crank pin 25. Follow-up tube 26 moves with piston 7, and the follow-up spool 27 pivots follow-up lever 28 about its connection with coupling 33, thus stroking the pilot valve in the opposite direction, and hydraulically stroking the servo valve to return it to its neutral position where it will hold the pitch at the command setting. To achieve accurate pitch settings, and to avoid putting on or taking off non-ordered pitch, it will be apparent that there must be a fixed relationship between the current pitch setting and the corresponding position of follow-up spool 27. This means that variations in the length of follow-up tube 26 cannot be tolerated. As previously mentioned, in other known constructions the follow-up tube comprises a plurality of concentric tubes through which the power oil is passed to the servo cylinder. Therefore, changes in power oil temperature caused thermal expansion and contraction of the follow-up tube assembly. In the arrangement disclosed in FIG. 1, the poer oil is passed instead through oil tubes 10, 11 and 11, which are radially removed from the follow-up tube 26, and since each oil tube in each section is free-floating at one of its ends, expansion and contraction of the oil tubes does not affect the overall length of the tube bundle assembly or, more importantly, the follow-up tube 26. Although the power oil in the illustrated embodiment does contact the followup tube at 9 and 13, these areas are of such short lengths relative to the overall length of the follow-up tube that the effect is substantially negligible. Both the propeller shaft 3 and the hub I normally will be filled with hub oil, and therefore the follow-up tube, being submerged in hub oil and removed from the power oil tubes, is in a relatively stable temperature environment, and its length remains substantially constant. There will be heat exchange between the power oil tubes and the hub oil, but because of the relative volumes, the heat from the power oil is widely dissipated in the hub oil to the extent that there is no substantial adverse effect on the follow-up tube.

It should be noted that only two tube bundle sections have been illustrated in FIG. 1 (tubes 10 and 11 being in one section and tubes 10' and 11 being in the other section), but in an actual vessel there will be many more such sections, and the overall length will be very much greater than the exaggerated short length shown in FIG. 1. Also, each tube section will normally include more than two power oil tubes. Thus, a typical tube section will include two tubes 10 and two tubes 11, the four tubes being circumferentially spaced in the bundle for good rotational balance, and all being radially outward of the central follow-up tube 26. The number of tube sections and the length of each section will, of course, vary with the particular vessel, but an exemplary construction might include five tube bundle sections between the hub and the servo box, typical lengths of these-sections being from approximately 19 feet to 25 feet. The power oil in such a construction might contact the follow-up tube over a length of perhaps 2 feet at the servo valve and perhaps the same length at the hub. This sectionalized tube bundle construction, in addition to its primary importance in avoiding false feedback indications, also permits substantial improvements in fabrication, assembly and disassembly, and maintenance.

As previously mentioned, some constructions, particularly for the United States Navy, must incorporate an air system for passing pressurized air to the propeller blades, where it is discharged along the leading edge of each blade on both blade faces. FIG. 1 also illustrated an improved arrangement for conveying such air to the blades. An air tube 29, adapted for connection to a source of pressurized air at its right end, passes through a simple rotary seal in the wall of servo box 5, and 'completely through the follow-up tube 26, passing also through seals in the piston 7 and the aft wall of the servo cylinder 6 to the hub end cap where it is rigidly coupled at 30. A series of rigid pipes or tubes, one of which is indicated schematically at 31, convey the air to individual blades from the hub connection 30. As will be illustrated in detail in other figures, the air passages from the hub connection 30 include generally horizontally disposed check valves for precluding entry of sea water when the air system is not in operation. Also as will be shown in more detail in subsequent figures, the air passages'communicate with annular air passages in the palm or blade disc of each blade, from whence the air passes outwardly to the outlet orifices along the blade edges. It will be seen that the air circuit from the air tube inlet to the blade palms is essentially hard coupled, and contains no swivel joints or so-called dynamic seals. The air tube is rigidly held in the hub, and is free to expand in the forward direction. Suitable radial projections on the air tube support the air tube concentrically within the follow-up tube 26. The follow-up tube 26 can be insulated from the air tube 29 by maintaining an annular oil column between the two tubes and/or by wrapping the air tube with an insulating tape. Also, in an actual construction, it will be advantageous to provide for automatic pressurization of the hub oil when the air system is activated so as to prevent the possibility of air being pumped into the hub or tubes should a leak occur in the air system.

Referring now to the further figures, FIG. 2A shows exemplary details of the hub end of a controllable pitch propeller in accordance with the invention. Corresponding reference characters relative to FIG. 1 have been used where feasible, so as to facilitate an understanding of the relationship between FIG. 2A and the more diagrammatic showing in FIG. l.-In FIG. 2A, the hub 1 carries a propeller blade 2 rotatably mounted in the hub wall by a blade crank disc 37 having crank pins, one'of which is shown at 25. The hub is mounted on the propeller shaft 3. Servo motor piston 7 is slidably mounted in cylinder 6. The particular mechanism illustrated in FIG. 2A is a double-crank type arrangement, that is, both the cylinder and piston are movable under the influence of the power oil, and each is coupled by a rod or the like with a crank pin carried by the crank disc of the blade. Thus, in FIG. 2A the cylinder is operatively coupled to, crank pin 25 through an actuating connection indicated by reference characters 23', 24, and the piston is operatively coupled with another crank pin through an actuating mechanism indicated by the reference characters 23, 24. The dual crank pins are commonly referred to as right-hand and left-hand, and are mounted on opposite sides of the crank disc relative to its axis of rotation. It will be apparent that the piston and cylinder move in opposite directions under the influence of the power oil, and hence the two crank pins will similarly be moved in opposite directions. Such a double crank mechanism for controllable pitch propellers is well known in the art, and an exemplary such mechanism is shown in FIGS. 4-6 of U.S. Pat. No. 3,171,494.

Still referring to FIG. 2A, the oil tubes 10 and 1 l, the followup tube 26, and the air tube 29 are shown approaching the hub1on the right-hand side. The oil tubes and the follow-uptube are coupled to cross-over coupling 14, and air tube 29 merely passes slidably through this coupling. At cross-over coupling 14, oil tube 10 is connected with the annular space between oil tube/piston rod 8 and oil tube/piston rod 9, which annular space connects with the right-hand side of cylinder 6 at 39. Oil tube 11 is connected at coupling 14 with the interior of oil tube 9, whereby oil in tube 11 will pass through coupling 14 and into the annulus between oil tube 9 and air tube 29, and thence into the left-hand side of cylinder 6 through an oil passage indicated at 38. It will be readilyapparent that, apart from air tube 29 which is rigidly coupled to the hub end at 30, the entire tubular assembly extending into the hub is coupled with piston 7 for movement therewith. It will also be apparent that the tubular assembly moves oppositely relative to the movement of cylinder 6.

Air tube 29 communicates at 30 with air passages in the form of rigid piping, one of which is shown at 31. This air passage extends radially outwardly from connection 30, and then axially along the outer wall of the hub, and communicates with an annular air passage 35 in the palm of blade 2. An air passage shown schematically at 36 communicates with annular air passage 35, and conducts the pressurized air along the leading edge of the blade, where it is discharged through orifices opening onto both blade faces. A check valve 34 is mounted in each air passage in a section of the hub, so as to prevent entry of sea water when the air system is not in operatiomAs shown in FIG. 2A, check valve 34 I is disposed generally horizontally so as to minimize the effects of centrifugal force, and in constructions where it is not feasible to orient the check valve generally horizontally, it should be oriented such that centrifugal force would tend to close it rather than open it. In the particular illustrated example, the valve is at a slight angle to the horizontal, but the angle is such that centrifugal force would tend to close the valve.

Referring now to FIG. 23, this shows the servo control end which may be used with the mechanism of FIG. 2A. FIG. 2B shows a servo valve box 5' of the shaft mounted type, as opposed to the gear mounted type of FIG. 1. Again, this is a well known servo valve control arrangement, andin fact may be considered as substantially identical in principle and operation with the servo valve control of U.S. Pat. No. 2,679,233. In the structure illustratedirl FIG. 2B, the propeller shaft extends on toward the right where it is coupled with the main reduction gear of the vessel. V

In FIG. 2B the servo valve body 17' includes a valve spool 18', controlling oil passages 21' and 22. A command pitch setter 32', which may be driven in any standard manner, is coupled to differential lever 28' through a linkage 33', the differential lever 28' being operatively associated with follow-up spool 27' in the usual manner- When command pitch setter 32' is driven, link 33' is caused to pivot differential lever 28' about its coupling with spool 27', so as to stroke valve spool 18' appropiately to pass power oil to passage 21' or passage 22', and hence drive the servo motor piston to the new pitchsetting. The valve is returned to its neutral positionwhen movement of the follow-up spool 27' pivots differential lever 28' about its coupling with arm 33'.

When power oil is admitted to oil passage 22', it passes into a hollowspace in the shaft, and then into the annulus between air tube 29 and follow-up tube 26 until it reaches cross-over coupling 16, where the oil is routed into oil tube 11. In FIG. 2B, the arrows indicate the ruturn flow of oil when passage 22' is connected to drain. When power oil is admitted to passage 21', it passes into the annulus between the hollow shaft and the follow-up tube 26, and thence to cross-over coupling 16, where it is routed into oil tubes 10'. A hub oil inlet connection is shown at 41.

In the mechanism of FIG. 28, it. will be noted that the piston movement is transmitted by the tubular assembly to cross-over coupling 16, and thence to the followup spool 27' by a follow-up link 40 which is operatively coupled to crossover coupling 16. It will be noted that in this embodiment there is no contact between the power oil and any part of the follow-up linkage in the area of the servo valve.

Air tube 29, of course, passes on through the propeller shaft to an appropriate point for connection to a pressurized air source.

FIG. 3 is an enlarged detailed illustration of a typical coupling 15 for the tube assembly. In FIG. 3, as well as in FIGS. 4 and 5, the arrows indicate the oil flow during a setting of the valve of FIG. 2B in which oil passage 21 in FIG. 2B is connected to the power oil inlet, and oil passage 22 is connected to drain. In FIG. 3, it will be noted that the left-hand tubes, tubes 10 and 11, have their ends slidably mounted in coupling 15 so as to absorb thermal expansion and contraction of the tubes without affecting the length of the overall tube assembly or the follow-up tube 26 in particular. The righthand oil tubes, tubes 10' and 11, are rigidly coupled to the coupling 15. The adjacent sections of follow-up member 26 are, of course, rigidly coupled at their adjacent ends in coupling 15.

FIG. 4 is an enlarged detailed illustration of a typical cross-over coupling 16, in which oil tubes 10 and 11 are slidably mounted, and to which follow-up member 26 is rigidly coupled. Link 40, it will be recalled, is coupled at its other end to the follow-up spool of FIG. 2B.

. It will be noted thatthe air tube 29 also is slidably mounted within the coupling 16 so that any expansion or contraction thereof will'not affect the length of the follow-up tube assembly, and so that the assembly is free to move back-and-forth relative to the air tube.

FIG; 5 is an enlarged detailed illustration of a typical cross-over coupling 14 adjacent the propeller hub. Since oil tubes 10 and 11 are slidably mounted at their right-hand ends in the adjacent coupling (not shown) they are rigidly coupled to coupling 14. Air tube 29 is, of course, slidably mounted in coupling 14, and followup member 26 is rigidly coupled thereto. The members which connect the servo motor piston with cross-over coupling 14 are rigidly connected to coupling 14.

In all the illustrated constructions, the feedback or follow-up linkage assembly between the servo motor in the hub and the follow-up spool at the servo valve box is relatively isolated from the temperature effects of the power oil in the oil tubes, and-hence the feedback assembly avoids the errors caused by substantial expansion and contraction that haved plagued the art of controllable pitch propellers.At the same time, substantial advantages in fabrication, assembly and maintenance have been achieved. It will be understood, however, that the invention itself can be embodied in construcand illustrated herein.

As mentioned previously, my invention also may provide for controlling the temperature of the follow-up tube by circulating controlled temperature oil continuously along the follow-up tube. An exemplary arrangement for carrying out this concept in a propeller mechanism of the type shown in FIG. 1 is illustrated in FIGS. 6-8. Although the embodiment illustrated in these figures includes the air tube arrangement for passing air to the propeller blades, it will be understood that the oil circulation feature of the invention may be utilized with or without the air tube. Referring now to these figures, the basic propeller mechanism is substantially identical to that disclosed in FIG. 1, but slightly modified to facilitate the oil circulation. Thus, the basic mechanism includes the follow-up tube 26, through which passes the air tube 29, having an air inlet rotary seal 62 at its forward end. As best shown in FIG. 7, the annulus 50 between the follow-up tube 26 and the air tube 29 is subdivided by two fins 53 and 54 into an in oil passage 51 and out" oil passage 52, the fins 53 and 54 thus functioning as a flow divider for oil fed into and returning from the assembly. An oil seal housing is shown schematically at 61 in FIG. 6 and, an exemplary oil seal arrangement is illustrated in more detail in FIG. 8,which will be discussed subsequently. Referring still to FIG. 6, a hydraulic pump 57 is driven by an electric motor 56, and is connected on its inlet side with oil in an oil reservoir 55 through an inlet pipe 58 and a suction strainer 59. The pump outlet is connected to the oil seal housing 61 through piping 60, whereby oil is passed from the pump to the oil seal 61, and thence into oil passage 51 in the annulus 50. The oil will flow through passage 51 to the hub, where it is transferred to the return oil passage 52, then back to the oil seal housing 61, and thence through return oil piping and a heat exchanger 65 back to the oil reservoir 55. Conveniently, a transfer passage between oil passages 51 and 52 at the hub end can be formed simply by terminating the fins 53 and 54 short of the piston in the hub, as indicated schematically at 53 in FIG. 6. Alternatively, the fins could be continued throughout the length of the air tube, to which they are connected, and transfer orifices could be formed in the fins adjacent the propeller hub. A conventional sliding seal is, of course, provided between the air tube and the piston of the hydraulic motor in the hub. In any event, regardless of the particular structure used, the oil from pump 57 traverses substantially the entire length of the follow-up tube through passage 51, and in or adjacent the hub the oil passes into out" passage 52 through which the return oil traverses again substantially the entire length of the follow-up tube. Of course, additional fins could be carried by air tube 29 if further flow division is desired. To control the temperature of the circulating oil, exemplary controls include a thermostat controlled oil heater 68, a heat exchanger 65, a heat exchanger bypass valve 64, and a thermostat controlled valve 66 with a thermostat bulb 67, valve 66 serving automatically to control the heat exchange fluid which is circulated through heat exchanger 65. Bypass valve 64 may be either manually or automatically controlled. It is to be understood that the temperature control arrangement of FIG. 6 is merely exemplary, and any convenient temperature control arrangement could be utilized with equal effectiveness.

Referring now to FIG. 8, an exemplary rotary oil seal is illustrated. The exemplary seal comprises a housing 69 which may, for instance, be mounted in the wall of the servo box. Housing 69 includes oil inlet and outlet passages 70 and 73, respectively. A cylindrical sleeve or the like 74 is carried by air tube 29 and rotatably journaled in housing 69. Sleeve 74 includes an inlet oil passage 71 and an outlet passage 72 continuously communicating with the corresponding passages and 73 of housing 69. Passages 71 and 72 open, respectively, into oil passages 51 and 52 in the annulus 50 between the air tube and the follow-up tube. As shown in FIG. 8, the divider fins 53 and 54 abut the sleeve 74 so as to maintain passages 51 and 52 separate. Suitable sliding seals are, of course, provided between sleeve 74 and the inner wall of follow-up tube 26 so as to allow for free relative movement between the two during pitch changes or upon thermal expansion and contraction of the air tube. It will be understood that any convenient rotary oil seal could be used, and the arrangement of FIG. 8 is merely exemplary.

If the circulating oil is fed into the follow-up member at a substantially constant temperature, then the temperature of the follow-up member will stabilize at or near the temperature of the oil. In one preferred manner of use, the controlled temperature oil can be circulated through the follow-up tube for a period of time, before the vessel gets underway, sufficient to raise the temperature of the follow-up tube and stabilize it. Thereafter, when the vessel is underway, the continuously circulating oil will function to either heat or cool the follow-up member as may be needed so as to maintain it at or close to the temperature for which it was calibrated. For instance the oil temperature controls might be set to maintain the oil in the reservoir at perhaps During circulation of this oil before start up of the vessel, the oil normally would be heating the follow-up tube so as intentionally to raise and stabilize its temperature at or near 100. Thereafter, should the temperature of the hub oil rise above 100 because of heat transfer from the power oil for the pitch changing motor, the circulating oil would be extracting heat from the follow-up member. During operation of the air system, the air passing down the air tube might be at a temperature of perhaps and the circulating oil then would carry off the excess heat from the air tube, so as to prevent its raising the temperature of the follow-up tube. These temperature figures are, of course, merely exemplary, but the important point is that feed back errors are eliminated due to varying temperatures.

In those propeller arrangements where the air tube is not used, the oil circulation system would still be usable and advantageous. Thus, where there is no air tube inside the follow-up tube a divider fin could easily be incorporated to span the radius of the follow-up tube, and hence to act as a flow divider for oil fed into and returning from the assembly. Also, in embodiments such as illustrated in FIGS. 2A and 28 where the end portions of the annulus beyond the transition or cross over couplings are used as passages for power oil, the circulating oil could conveniently be introduced into the follow-up tube/air tube annulus at the forward cross-over coupling, then transferred to the other passage of the annulus at the after cross-over coupling, and then removed from this latter passage again at the forward cross-over coupling. A suitable sealing arrangement at the forward cross-over coupling is well within the skill of the art.

The disclosure of U.S. Pat. Nos. 3,257,186; 3,171,494; and 2,679,233 are herein incorporated by reference.

The invention has been described indetail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. In a marine vessel, a controllable pitch propeller, a propeller hub, a plurality of controllable pitch proeller blades mounted on said hub, a hollow propeller shaft of substantial length coupled to said hub and adapted for operative connection to a power plant for the vessel, a hydraulic motor located at least near the hub for varying and controlling the pitch of said blades, means defining oil passages extending down said shaft for conveying power oil to said hydraulic motor, valve means for controlling the flow of oil through said oil passages, and means forming a follow-up link of substantial length extending down said hollow shaft but physically removed from said oil passages over at least themajor part of the length of said link so as to minimize direct heat transfer therebetween, said follow-up link being operatively coupled to said hydraulic motor for movement therewith such that the instantaneous position of a selected point located on said follow-up link a substantial distance from said hydraulic motor is indicative of the instantaneous actual pitch setting of said blades substantially regardless of the temperature of the oil in said oil passages.

2. Apparatus as claimed in claim 1 wherein said hydraulic motor comprises a piston and cylinder, and is located inside said hub.

3. Apparatus as claimed in claim 2 wherein said oil passages comprise oil tubes extending down said hollow shaft and communicating at their forward ends .with passages leading from said shaft to said valve means.

4. Apparatus as claimed in claim 3 wherein said follow-up link, over at least the major part of its length, is substantially centrally disposed in said hollow shaft, and said oil tubes, over at least the major part of their lengths, are disposed radially outwardly of said followup link.

5. Apparatus as claimed in claim 4 wherein said oil tubes and said follow-up link are coupled together as a nested assembly movable with said hydraulic motor,

and wherein said assembly includes means for absorbing any expansion or contraction of said oil tubes so as not to affect the length of said follow-up link.

6. Apparatus as claimed in claim 5 wherein said nested assembly comprises a plurality of longitudinally disposed sections extending down said hollow shaft, each section being joined to adjacent sections by couplings, each section of said follow-uplink being rigidly connected to adjacent couplings, and each section of oil tube of at least most of the sections being slidably mounted in at least one of the adjacent couplings, whereby any expansion or contraction of a section of oil tube is absorbed in that section of the assembly, and the length of the assembly between the forward-most ,and after-most couplings is governed solely by the length of the follow-up linkage therebetween.

7. Apparatus as claimed in claim 1 further comprising a selectively operable pitch command means, and

control means operatively coupled to said command means, said valve means and said follow-up means for variably setting said valve means appropriately to obtain and maintain conformity between desired pitch settings indicated by said command means and actual pitch settings indicated by said follow-up link.

SLApparatus as claimed in claim 7 wherein said control means comprises a differential lever coupled to said follow-up link at a substantial distance from said hydraulic motor.

9. Apparatus as claimed in claim 1 further comprising an air tube extending down said hollow shaft and being rigidly coupled to said hub at its stem end and adapted for connection to a pressurized air source at its forward end, and means defining hub air passages extending from the rigidly coupled end of said air tube to each of said blades for dischargeof air through orifices opening therefrom.

10. Apparatus as claimed in claim 9 wherein said follow-up link is of hollow tube construction, and said air tube passes therethrough and through said hydraulic motor to said rigid coupling at the stern end of said hub, said follow-up link being freely movable relative to said air tube. i

11. Apparatus as claimed in claim 10 wherein each blade includes a crank disc formed with an annular air passage encircling the pitch-changing rotational axis of the blade, and one of said hub air passages from said air tube opens into each annular air passage.

12. Apparatus as claimed in claim 11 wherein each hub air passage includes a check valve closely adjacent but upstream of said annular air passage, said valve being oriented relative to the rotational axis of said hub such that any substantial centrifugal biassing of the valve will be in a direction other than its opening direction.

13. Apparatus as claimed in claim 1 wherein said oil passages comprise tubes in said hollow shaft, and wherein, over the major portion of their lengths, the oil tubes and said follow-up link comprise a-unitary bundle movable together back-and-forth in said hollow shaft in response to movement of said hydraulic motor, the oil tubes and the follow-up link being radially spaced from each other, the bundle being divided longitudinally into in the associated coupling member such that expansion and contraction of an oil tube is absorbed in the slidable mounting without varying the length of the section.

14. Apparatus as claimed in claim 1 further comprising means for circulating fluid at a controlled temperature along at least part of the length of, and in contact with, said follow-up link.

15. Apparatus as claimed in claim 14 wherein said follow-up link is of hollow tubular form, and said controlled temperature fluid circulates in the hollow interior of said follow-up link.

16. Apparatus as claimed in claim 10 further comprising means for circulating fluid at a controlled temperature in the annulus between said hollow tube follow-up link and said air tube to control the temperature of said follow-up link.

17. Apparatus as claimed in claim 16 including means extending along the length of said annulus for dividing the annulus into separate flow passages communicating with each other at the after end of the annulus, and wherein said circulating means comprises means for passing controlled temperature fluid into one of said flow passages at the forward end thereof and for receiving return fluid from the other of said passages at the forward end thereof, whereby the circulating fluid traverses the length of said annulus.

18. Apparatus as claimed in claim 17 wherein said circulating means includes selectively operable heating and cooling means for said fluid.

19. ln a controllable pitch propeller for a marine vessel, a propeller hub, a plurality of controllable pitch propeller blades mounted on said hub, a hollow propeller shaft coupled to said hub and adapted for operative connection to a power plant for the vessel, a hydraulic motor comprising a piston and cylinder located in the hub for varying and controlling the pitch of said blades, means defining oil passages extending down said shaft for conveying power oil to said hydraulic motor, means defining a follow-up link of hollow tubular construction in said hollow shaft operatively coupled to said hydraulic motor for movement therewith, an air tube extending down said hollow shaft through said follow-up link and the piston and cylinder of said hydraulic motor and rigidly coupled to said hub at the stern end thereof, and adapted for connection to a pressurized air source at the forward end thereof, and means defining air passages from the rigidly coupled end of said air tube to the propeller blades for discharge of air through orifices opening from the blades.

20. Apparatus as claimed-in claim 19 further comprising means for circulating fluid at a controlled temperature through the annulus between said hollow tube follow-up link and said air tube to control the temperature of said follow-up link.

21. Apparatus as claimed in claim 20 incuding means forming forward-to-aft and aft-to-forward fluid passages in said annulus along the length thereof, said passages communicating at their aft ends, and wherein said circulating means passes fluid to and receives fluid from said passages at the forward ends thereof.

22. In a marine vessel, a controllable pitch propeller, a propeller hub, a plurality of controllable pitch propeller blades mounted on said hub, a hollow propeller shaft of substantial length coupled to said hub and adapted for operative connection to a power plant for the vessel, means for varying and controlling the pitch of said blades, means forming a movable follow-up linkage of substantial length extending down said hollow shaft and operatively associated with said propeller blades such that the instantaneous position of a selected point located on said follow-up linkage a substantial distance from said hub is indicative of the instantaneous actual pitch setting of said blades, and means for circulating controlled temperature fluid along at least a substantial part of the length of, and in contact with, said follow-up linkage so as to control the temperature thereof and minimize the possibility of erroneous pitch setting indications caused by thermal expansion and contraction of the follow-up linkage. 

1. In a marine vessel, a controllable pitch propeller, a propeller hub, a plurality of controllable pitch proeller blades mounted on said hub, a hollow propeller shaft of substantial length coupled to said hub and adapted for operative connection to a power plant for the vessel, a hydraulic motor located at least near the hub for varying and controlling the pitch of said blades, means defining oil passages extending down said shaft for conveying power oil to said hydraulic motor, valve means for controlling the flow of oil through said oil passages, and means forming a follow-up link of substantial length extending down said hollow shaft but physically removed from said oil passages over at least the major part of the length of said link so as to minimize direct heat transfer therebetween, said follow-up link being operatively coupled to said hydraulic motor for movement therewith such that the instantaneous position of a selected point located on said follow-up link a substantial distance from said hydraulic motor is indicative of the instantaneous actual pitch setting of said blades substantially regardless of the temperature of the oil in said oil passages.
 2. Apparatus as claimed in claim 1 wherein said hydraulic motor comprises a piston and cylinder, and is located inside said hub.
 3. Apparatus as claimed in claim 2 wherein said oil passages comprise oil tubes extending down said hollow shaft and communicating at their forward ends with passages leading from said shaft to said valve means.
 4. Apparatus as claimed in claim 3 wherein said follow-up link, over at least the major part of its length, is substantially centrally disposed in said hollow shaft, and said oil tubes, over at least the major part of their lengths, are disposed radially outwardly of said follow-up link.
 5. Apparatus as claimed in claim 4 wherein said oil tubes and said follow-up link are coupled together as a nested assembly movable with said hydraulic motor, and wherein said assembly includes means for absorbing any expansion or contraction of said oil tubes so as not to affect the length of said follow-up link.
 6. Apparatus as claimed in claim 5 wherein said nested assembly comprises a plurality of longitudinally disposed sections extending down said hollow shaft, each section being joined to adjacent sections by couplings, each section of said follow-up link being rigidly connected to adjacent couplings, and each section of oil tube of at least most of the sections being slidably mounted in at least one of the adjacent couplings, whereby any expansion or contraction of a section of oil tube is absorbed in that section of the assembly, and the length of the assembly between the forward-most and after-most couplings is governed solely by the length of the follow-up linkage therebetween.
 7. Apparatus as claimed in claim 1 further comprising a selectively operable pitch command means, and control means operatively coupled to said command means, said valve means and said follow-up means for variably setting said valve means appropriately to obtain and maintain conformity between desireD pitch settings indicated by said command means and actual pitch settings indicated by said follow-up link.
 8. Apparatus as claimed in claim 7 wherein said control means comprises a differential lever coupled to said follow-up link at a substantial distance from said hydraulic motor.
 9. Apparatus as claimed in claim 1 further comprising an air tube extending down said hollow shaft and being rigidly coupled to said hub at its stern end and adapted for connection to a pressurized air source at its forward end, and means defining hub air passages extending from the rigidly coupled end of said air tube to each of said blades for discharge of air through orifices opening therefrom.
 10. Apparatus as claimed in claim 9 wherein said follow-up link is of hollow tube construction, and said air tube passes therethrough and through said hydraulic motor to said rigid coupling at the stern end of said hub, said follow-up link being freely movable relative to said air tube.
 11. Apparatus as claimed in claim 10 wherein each blade includes a crank disc formed with an annular air passage encircling the pitch-changing rotational axis of the blade, and one of said hub air passages from said air tube opens into each annular air passage.
 12. Apparatus as claimed in claim 11 wherein each hub air passage includes a check valve closely adjacent but upstream of said annular air passage, said valve being oriented relative to the rotational axis of said hub such that any substantial centrifugal biassing of the valve will be in a direction other than its opening direction.
 13. Apparatus as claimed in claim 1 wherein said oil passages comprise tubes in said hollow shaft, and wherein, over the major portion of their lengths, the oil tubes and said follow-up link comprise a unitary bundle movable together back-and-forth in said hollow shaft in response to movement of said hydraulic motor, the oil tubes and the follow-up link being radially spaced from each other, the bundle being divided longitudinally into sections coupled together by coupling members, the follow-up link of each section being rigidly coupled to the adjacent coupling members and the oil tubes of each section having at least one end slidably mounted in the associated coupling member such that expansion and contraction of an oil tube is absorbed in the slidable mounting without varying the length of the section.
 14. Apparatus as claimed in claim 1 further comprising means for circulating fluid at a controlled temperature along at least part of the length of, and in contact with, said follow-up link.
 15. Apparatus as claimed in claim 14 wherein said follow-up link is of hollow tubular form, and said controlled temperature fluid circulates in the hollow interior of said follow-up link.
 16. Apparatus as claimed in claim 10 further comprising means for circulating fluid at a controlled temperature in the annulus between said hollow tube follow-up link and said air tube to control the temperature of said follow-up link.
 17. Apparatus as claimed in claim 16 including means extending along the length of said annulus for dividing the annulus into separate flow passages communicating with each other at the after end of the annulus, and wherein said circulating means comprises means for passing controlled temperature fluid into one of said flow passages at the forward end thereof and for receiving return fluid from the other of said passages at the forward end thereof, whereby the circulating fluid traverses the length of said annulus.
 18. Apparatus as claimed in claim 17 wherein said circulating means includes selectively operable heating and cooling means for said fluid.
 19. In a controllable pitch propeller for a marine vessel, a propeller hub, a plurality of controllable pitch propeller blades mounted on said hub, a hollow propeller shaft coupled to said hub and adapted for operative connection to a power plant for the vessel, a hydraulic motor comprising a piston and cylinder located in the hub for varying and controLling the pitch of said blades, means defining oil passages extending down said shaft for conveying power oil to said hydraulic motor, means defining a follow-up link of hollow tubular construction in said hollow shaft operatively coupled to said hydraulic motor for movement therewith, an air tube extending down said hollow shaft through said follow-up link and the piston and cylinder of said hydraulic motor and rigidly coupled to said hub at the stern end thereof, and adapted for connection to a pressurized air source at the forward end thereof, and means defining air passages from the rigidly coupled end of said air tube to the propeller blades for discharge of air through orifices opening from the blades.
 20. Apparatus as claimed in claim 19 further comprising means for circulating fluid at a controlled temperature through the annulus between said hollow tube follow-up link and said air tube to control the temperature of said follow-up link.
 21. Apparatus as claimed in claim 20 incuding means forming forward-to-aft and aft-to-forward fluid passages in said annulus along the length thereof, said passages communicating at their aft ends, and wherein said circulating means passes fluid to and receives fluid from said passages at the forward ends thereof.
 22. In a marine vessel, a controllable pitch propeller, a propeller hub, a plurality of controllable pitch propeller blades mounted on said hub, a hollow propeller shaft of substantial length coupled to said hub and adapted for operative connection to a power plant for the vessel, means for varying and controlling the pitch of said blades, means forming a movable follow-up linkage of substantial length extending down said hollow shaft and operatively associated with said propeller blades such that the instantaneous position of a selected point located on said follow-up linkage a substantial distance from said hub is indicative of the instantaneous actual pitch setting of said blades, and means for circulating controlled temperature fluid along at least a substantial part of the length of, and in contact with, said follow-up linkage so as to control the temperature thereof and minimize the possibility of erroneous pitch setting indications caused by thermal expansion and contraction of the follow-up linkage. 